This invention relates to pick holders and the combination thereof with picks and is particularly concerned with the art of mineral mining picks (which term, as is generally acknowledged in the art, includes picks for rock mining and road planing). In this art the pick holder is likely to be in the form of a socketed block or box on or in a driven component of a mining machine but may be the component itself.
The invention is concerned with picks and pick holders of the type in which, during their use, a fluid (usually water and conveniently referred to as such hereafter) is directed into the cutting region of the picks for the primary purposes of dust suppression, flushing and cooling (which latter term includes cooling incendive sparking). Examples of picks and pick holders of this general type are disclosed in our G.B. Specification No. 2,088,441 which is concerned with the way in which the flow of water under pressure can be achieved through the pick (for the aforementioned purposes) in an efficient manner. The advantages of providing a relatively simple and efficient means of achieving flow of water under pressure through a pick and the appropriate application of the resultant water spray or jet for the aforementioned purposes are discussed in our GB Specifications Nos. 2,088,441 and 82 03 638. It is most desirable that the water spray or jets emanating from the pick and pick holders are utilised efficiently and controlled to alleviate the presence of excessive water at the mineral mining site. With this in mind it has hitherto been proposed to incorporate in the mineral mining machinery valve means by which water supply for dust suppression, flushing or cooling is provided only when required for those purposes. In a conventional coal shearer drum the picks are secured in holding blocks which are helically spaced around the peripheral edge of a helical web or flange on the drum. During rotation of the drum for cutting, the picks are only in engagement with the mineral face for a minor arcuate portion of the drums rotation and in a prior proposal the valve means is incorporated in the drum to restrict the supply of water so that the spray or jets are provided only for those picks which at a given instant are passing through the aforementioned minor cutting arc. It has also been proposed to provide water sprays or jets from nozzles on picks and pick holders and to have valve means in the holder or carried by the pick which is responsive to pressure of cutting on the pick so that a water supply is available for the spray or jet on that pick or holder only for the period during which the pick is in cutting engagement with the mineral face; examples of these proposals are to be found in European Specifications Nos. 0 010 534 and 0 060 827 and in G.B. Specification No. 2,077,813 A.
The valve means in the prior proposals of the European Specifications are relatively complicated in operation and design, expensive to manufacture and assemble and because of their complicated structure (which calls for precision made valve components) will require frequent servicing and replacement. Where it is proposed that the valve means is carried by the pick (as in European No. 0 060 827) it will be realised, because of the limited useful working life expected for mineral mining picks, the aforementioned considerations of cost and complexity of design are likely to render the proposal particularly unattractive and unacceptable commercially.
The proposal in the aforementioned G.B. No. 2,077,813A is for a relatively simple form of valve means comprising a resilient sleeve on the pick shank which sleeve is deformed in response to cutting pressure on the pick to admit water to the nozzle. A necessary feature of this proposal is that the socket in the pick box which receives the pick shank is enlarged to permit the required deformation of the sleeve; this calls for expensive machining of the box and has the further disadvantage that the cavity within which the sleeve is received can collect coal (or like) dust which will impair the resilient deformation of the sleeve. There are the further disadvantages that the sleeve will likely have a very short useful life, will exhibit poor sealing characteristics, and may easily be damaged during handling of the pick and its insertion into the pick box by virtue of its exposed position on the pick shank.
It is an object of the present invention to provide a holder for a pick and the combination of a pick and holder which provides for water supply through the pick for dust suppression, flushing or cooling purposes during cutting and also provides a relatively simple, inexpensive and efficient means of controlling that water supply in a manner which alleviates the disadvantages of the aforementioned prior proposals.